DC/DC converter

Abstract

A DC/DC converter includes a main switching element and a subordinate switching element, and is arranged to supply power to load via a coil. The ON-time of a subordinate switching element in a succeeding cycle is controlled based on a period of time tdif from the time when the subordinate switching element is turned off until the time when voltage at the point of connection of the two switching elements reaches a predetermined threshold value.

1. A DC/DC converter comprising two switching means connected in series, and a coil connected to a point of connection between the two switching means, and being arranged to convert a direct current input voltage to a predetermined direct current output voltage and supply power to load via the coil,
 the DC/DC converter further comprising control unit configured such that when the switching means turned on during accumulation of energy in the coil is main switching means, and the switching means turned on during delivery of the energy accumulated in the coil to an output side is subordinate switching means, an ON-time of the subordinate switching means in a succeeding cycle is controlled based on a period of time from a time when the subordinate switching means is turned off until a time when a voltage at the point of connection of the two switching means reaches a predetermined threshold value. 
 
   
   
     2. The DC/DC converter according to  claim 1 , characterized in that
 the control unit is configured to control the ON-time of the subordinate switching means in the succeeding cycle such that a polarity of a current flowing through the coil is not inverted. 
 
   
   
     3. The DC/DC converter according to  claim 1 , characterized in that
 the ON-time of the subordinate switching means in the succeeding cycle is controlled based on a potential accumulated in a capacitor during the period of time from the time when the subordinate switching means is turned off until the time when the voltage at the point of connection of the two switching means reaches the predetermined threshold value. 
 
   
   
     4. The DC/DC converter according to  claim 3 , characterized in that
 the potential accumulated in the capacitor is controlled by a predetermined value in each cycle before the subordinate switching means is turned off. 
 
   
   
     5. The DC/DC converter according to  claim 1 , characterized in that
 the DC/DC converter is one of a step-down converter or a step-up converter. 
 
   
   
     6. The DC/DC converter according to  claim 1 , characterized in that
 the control unit adopts one or both of a PWM method or a PFM method in order to obtain a switching pulse for the main switching means.